Moldable bone graft compositions

ABSTRACT

The present disclosure relates to compositions useful in synthetic bone graft applications. Particularly, the disclosure teaches moldable bone graft compositions, methods of making the compositions, and methods of utilizing the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S. patentapplication Ser. No. 16/047,420, filed on Jul. 27, 2018, which issued asU.S. Pat. No. 10,835,642 on Nov. 17, 2020, which itself is aContinuation Application of U.S. patent application Ser. No. 15/395,301,filed on Dec. 30, 2016, which issued as U.S. Pat. No. 10,034,965 on Jul.31, 2018, which itself is a Continuation Application of U.S. patentapplication Ser. No. 14/939,902, filed on Nov. 12, 2015, which issued asU.S. Pat. No. 9,566,368 on Feb. 14, 2017, which itself claims thebenefit of priority to U.S. Provisional Patent Application No.62/079,047, filed on Nov. 13, 2014, each of which is hereby incorporatedby reference in its entirety for all purposes.

FIELD

The present disclosure relates to compositions useful in synthetic bonegraft applications. Particularly, the disclosure teaches moldable bonegraft compositions, methods of making said compositions, and methods ofutilizing the same.

BACKGROUND

Current bone grafting procedures include the use of autogenous bone as agraft material (i.e., “autografting”). Use of autogenous bone, however,subjects a patient to increased pain and discomfort, and an increasedrisk of infection, because it requires the patient to undergo additionalsurgery to recover the autogenous bone for use in the graftingprocedure.

Current bone grafting also includes the use of bone from a donor as agraft material (e.g., “allografting” from the same species or“xenografting” from a different species). Both allograft bone andxenograft bone, though from natural sources, subject a patient to therisk of disease transmission and graft rejection.

A third option in the field of bone grafting includes the use ofsynthetic bone graft material. Some synthetic bone graft material ismixed with autograft, allograft, or xenograft bone, and thus stillsubjects a patient to the risks above. Other disadvantages to currentsynthetic bone graft materials are: (1) the poor resorbability profileof many synthetic bone graft compositions, which leads to lowproliferation and remodeling of new bone throughout the defect site, (2)low bioactivity or other osteogenic effects, (3) the inability to moldor form the material into a desirable shape during intraoperativesurgical procedures, (4) the inability to maintain the desired placementat the defect site, (5) lack of antimicrobial properties, and (6) theinability to combine bone healing properties of different syntheticmaterials into a single implant.

As such, there is a great need in the art for an improved synthetic bonegraft material that is moldable, highly bioactive, and presents anoptimal resorbability profile that increases the proliferation andremodeling of new bone throughout a defect site.

SUMMARY OF THE DISCLOSURE

The present disclosure addresses the need in the medical community of asuperior synthetic bone graft material, by providing a moldable bonegraft composition that is: (1) moldable, to facilitate surgeon handlingand maintain placement of granules at the defect site; (2) bioactive, toinitiate immediate apatite layer formation and facilitate proliferationand remodeling of new bone throughout the defect site; (3)osteostimulative, to stimulate the proliferation and differentiation ofbone healing cells, (4) anti-microbial, to inactivate infectious agentscommon to surgical procedures, and (5) provides a gradual resorptionprofile between the soluble, faster resorbing β-TCP, and more stable,slower resorbing HA, in an optimized ratio in line with the hostremodeling process. The combination of bioactive glass, biphasicmineral, and resorbable polymer carrier addresses the intra-operativehandling needs of the surgeon, as well as the long and short termhealing demands of, for example, spine fusion procedures.

In aspects, the moldable bone graft composition of the present inventionis a bone void filler composition, which can optionally be loaded into adevice for filling bony voids or gaps of the skeletal system, and can beused in conjunction with autograft as a bone graft extender. The bonevoid filler of the present invention can be resorbed and replaced withhost bone during the healing process.

In an aspect, the disclosure provides for a moldable bone graftcomposition, comprising: about 40-80% by weight of one or morebioresorbable polymers; about 10-50% by weight of biphasic calciumphosphate particles comprising hydroxyapatite (HA) and beta-tricalciumphosphate (β-TCP); and about 1-40% by weight of at least one bioactiveglass, wherein said calcium phosphate particles and said bioactive glasstogether comprise about 20-60% by weight of the moldable bone graftcomposition.

In a particular aspect, the one or more bioresorbable polymers comprisea polyalkylene oxide polymer having a molecular weight of about 500-1500grams/mole, a specific gravity of about 1.0-1.3 (at 25° C.), and aviscosity of about 10-40 cSt (at 210° C.) using methods described in theUSP-NF monograph for Polyethylene Glycol. In this aspect, the polymerhas a melting temperature of about 38-50° C. measured by differentialscanning calorimetry.

In a particular aspect the alkylene oxide polymer is comprised of ablend of USP-NF grades of PEG 1450 and PEG 400, in a weight ratio ofabout 75:25 to 85:15.

In one aspect, the moldable bone graft compositions taught hereincomprise biphasic HA/β-TCP particles that contain about 20-60%hydroxyapatite and about 40-80% β-tricalcium phosphate.

In some aspects, the moldable bone graft compositions taught hereincomprise biphasic HA/β-TCP particles that contain about 60%hydroxyapatite and about 40% β-tricalcium phosphate.

In embodiments, the moldable bone graft compositions comprise calciumphosphate particles that have interconnected macro- and microporosity.

In some embodiments, the moldable bone graft composition comprisingcalcium phosphate particles has about 30-90% of the calcium phosphateparticles with a diameter of about 1000-2000 μm; about 10-70% of thecalcium phosphate particles with a diameter of about 425-1000 μm, about10-50% of the calcium phosphate particles with a diameter of about710-1000 μm; and about 1-30% of the calcium phosphate particles with adiameter of about 425-710 μm.

In embodiments, the moldable bone graft composition comprises 45S5bioactive glass. In embodiments, the bioactive glass is in the form ofparticles having a diameter of about 1-600 μm. In embodiments, thebioactive glass is in the form of particles having a diameter of about1-425 μm. In embodiments, at least 60%, or 70%, or 80%, or 90%, or 95%of the bioactive glass is in the form of particles having a diameter ofabout 212-420 μm.

In aspects, the bioactive glass is in the form of irregular granules. Inother aspects, the bioactive glass is in the form of approximatelyspherical particles. In yet other aspects, the bioactive glass is in theform of fibers.

In an embodiment, the moldable bone graft composition comprises calciumphosphate particles and bioactive glass, along with an alkylene oxidepolymer carrier, and about 60-90% of the calcium phosphate particles andbioactive glass together are in the form of particles having a diameterof about 425-2000 μm, and about 10-40% of the particles have a diameterof about 1-425 μm.

In certain aspects, the moldable bone graft composition is formulated asa single use composition having a mass of about 1.5 grams to about 30grams.

In some aspects, the moldable bone graft composition is in the form of asingle use composition. In some aspects, the single use moldable bonegraft composition has a volume of about 1-20 cc.

In certain aspects, the moldable bone graft composition has a density ofabout 1.2-1.8 g/cc.

In embodiments, the moldable bone graft composition is in the form of acylinder. In other aspects, the moldable bone graft composition is inthe form of a cubical shape.

In embodiments, the moldable bone graft composition has a crushresistance force of less than about 20 lbf, and a crush resistancestiffness of less than about 90 lbf/in, using a hand-held force gagewith a one-half inch platen. The device was tested in its finalcommercial form, approximately 15 grams of material, 0.62 inches indiameter and 2.0 inches in length. The force gage platen was placedapplied perpendicular to the long axis of the implant.

In embodiments, the moldable bone graft composition can be molded intoany desired shape without loss of homogeneity.

In aspects, a syringe applicator can be filled with the moldable bonegraft composition, in order to facilitate application of thecomposition. In certain aspects, the force required to eject themoldable bone graft composition from the syringe applicator is less than20 lbf using a hand held force gage with a one-half inch platen andsimulated use conditions, where the platen is applied to the pushrod ofthe syringe applicator to forcibly eject the bone graft from thesyringe. The device was tested in its final commercial form, 15 grams ofmaterial, 0.62 inches in diameter and 2.0 inches in length, loaded intoa 0.62 inch open barrel syringe.

In certain embodiments, the moldable bone graft compositions taughtherein further comprise a melt skin layer disposed on the outer surfaceof the composition, wherein the melt skin layer comprises abioresorbable polymer. In aspects, the melt skin serves to facilitateejection from the syringe and enhance the cosmetic appearance of theimplant.

In embodiments, the moldable bone graft composition comprises abioresorbable polymer that dissolves in phosphate buffered saline (PBS)at 37° C. at a rate of about 0.01-0.20 grams/minute, determined byplacing 15 grams of bone graft material in an ASTM E-11 45 micron sieve,submerging in 500 ml of circulating PBS, and measuring mass loss at 7.5,15, 30, 45 and 60 minutes.

In embodiments, the moldable bone graft composition comprises abioresorbable polymer that dissolves in PBS at 37° C. in about 60-600minutes, determined by placing 15 grams of bone graft material in anASTM E-11 45 micron sieve, submerging in 500 ml of circulating PBS, andmeasuring mass loss at 7.5, 15, 30, 45, 60 and 600 minutes.

In embodiments, the moldable bone graft composition comprises abioresorbable polymer that dissolves in PBS at 37° C. in less than 60minutes, determined by placing 15 grams of bone graft material in anASTM E-11 45 micron sieve, submerging in 500 ml of circulating PBS, andmeasuring mass loss at 7.5, 15, 30, 45 and 60 minutes.

In aspects, the disclosure teaches a moldable bone graft composition,comprising: about 50-70% by weight of one or more bioresorbablepolymers; about 25-40% by weight of biphasic calcium phosphate particlescomprising a blend of hydroxyapatite and tricalcium phosphate; and about1-15% by weight of at least one bioactive glass, wherein said calciumphosphate particles and said bioactive glass together comprise about30-50% by weight of the moldable bone graft composition.

In embodiments, the moldable bone graft compositions taught herein forma hydroxyapatite surface layer in simulated body fluid (SBF).

In embodiments, the moldable bone graft compositions taught hereinstimulate mesenchymal stem cell differentiation in MG63 osteosarcoma andC2C12 mesenchymal cell lines.

In embodiments, the moldable bone graft compositions taught hereinstimulate osteoblast cell proliferation in MG63 osteosarcoma and C2C12mesenchymal cell lines.

In embodiments, the moldable bone graft compositions taught hereindemonstrate antimicrobial efficacy according to methods based on USP<51> Antimicrobial Effectiveness Test.

In embodiments, the moldable bone graft compositions taught hereinprovide a spine fusion rate of greater than 50% in a New Zealand whiterabbit spine fusion model, as determined by radiographic analysis,manual palpation analysis and biomechanical analysis.

In embodiments, the moldable bone graft compositions taught hereinprovide a spine fusion rate of at least about 80% in a New Zealand whiterabbit spine fusion model, as determined by biomechanical range ofmotion analysis in flexion-extension.

In embodiments, the moldable bone graft compositions taught herein canbe used in a method to repair a bone defect. In aspects, the methodcomprises applying the moldable bone graft composition to a bone defectin a patient in need thereof. In some embodiments, the defect is aspinal bone defect. In some aspects, the bone defect is in theposterolateral gutter of a vertebral body.

In an embodiment, the moldable bone graft composition is bioactive. Inanother embodiment, the bioactive moldable bone graft compositioncomprises a biphasic mineral granulate of HA/β-TCP particles (1-2 mm)and bioactive glass (212-420 μm), which are suspended in an alkyleneoxide polymer carrier. In certain aspects, the aforementioned moldablebone graft composition is formulated as putty. In some embodiments, theaforementioned moldable bone graft composition exhibits synergisticeffects, which are greater than the additive effects that one wouldencounter utilizing biphasic HA/β-TCP based granulate or bioactive glassparticles alone. For example, the 45S5 bioactive glass particles,homogeneously dispersed between the biphasic mineral granulate, elicitan immediate and robust bioactive response, resulting in apatite layerformation and bone cell attachment on the bioactive glass surface. Thisresponse results in a more rapid recruitment and infiltration of bonehealing cells within the biphasic mineral granulate matrix, thusaccelerating and enhancing its own osteoconductive response. Inaddition, the initial bioactive response of the faster resorbingbioactive glass particles is supported and perpetuated by the moregradual resorbing biphasic granulate. Thus, the presence of bone healingelements due to the bioactive glass dispersed among the biphasic resultsin more rapid osteoconductivity and remodeling than would occur with thebiphasic granules alone.

In aspects, the moldable bone graft composition is optimized for boneremodeling in posterolateral spine fusion procedures. In aspects, themoldable bone graft compositions taught herein exhibit a gradualresorption rate, porosity, and microstructure, which result in a stablescaffold that allows sustained osteoconductivity during the healingprocess.

The moldable bone graft compositions of the present disclosure, incertain aspects, are a synthetic bone void filler device comprised ofbiphasic HA/β-TCP (60:40) calcium phosphate granules & 45S5 bioactiveglass particles suspended in a resorbable alkylene oxide polymer (AOP)carrier. In aspects, the moldable carrier allows the surgeon to shapeand apply the implant based on each patient's unique anatomy, and servesto maintain the placement of implant materials at the defect site untilclosure. Once implanted, the biocompatible, resorbable polymer carrieris excreted from the body through natural metabolic pathways. Inparticular applications, after implantation of the moldable bone graftcompositions, the 45S5 bioactive glass component undergoes a uniquesurface modification within the physiological environment that allowsfor direct bonding with surrounding bone through an exchange ofbiologically active ions, which produces a bioactive hydroxy carbonateapatite (HCA) layer to which bone can readily bond to. These surfacereactions are followed by the proliferation and differentiation of bonerelated cells on the apatite matrix as part of the normal healingprocess.

In embodiments, the biphasic mineral granules (1-2 mm) of the presentcompositions, combine the long term stability of slower resorbinghydroxyapatite (HA) with the solubility of faster resorbingbeta-tricalcium phosphate (β-TCP), in a ratio which the presentinventors have found to provide controlled implant resorption, resultingin more reliable bone remodeling at the defect site. Dissolution of thedisclosed biphasic mineral in biological fluids produces a directbonding interface with host bone through the release of calcium andphosphate ions and subsequent formation of a surface apatite layersimilar to bone mineral. In addition, the structural microporosity andmacroporosity of the disclosed biphasic granules are in the optimalranges needed to allow penetration of biological fluids (>10 μm) andsupport osteoconductivity (>100 μm), providing a more sustainedremodeling response at the defect site.

In embodiments, the disclosure provides bioactive bone graft putty thatis a bone void filler intended for use in bony voids or gaps, includingthose that are not intrinsic to the stability of the bony structure.These defects may be surgically created osseous defects or osseousdefects created from traumatic injury to the bone. In some embodiments,the bioactive bone graft putty may be packed gently into bony voids orgaps of the skeletal system (i.e., extremities, pelvis, andposterolateral spine fusion procedures). In some embodiments, thebioactive bone graft putty can also be used with autograft as a bonegraft extender in the posterolateral spine. In embodiments, thebioactive bone graft putty device provides bone void filler that isresorbed and replaced with host bone during the healing process.

In embodiments, the disclosure provide a bioactive bone graft putty thatis a synthetic bone void filler comprised of a blend of calciumphosphate materials (e.g., biphasic calcium phosphate granulescomprising hydroxyapatite and tricalcium phosphate) and bioactive glassgranules suspended in a resorbable polymer carrier that facilitateshandling and delivery of the granule components. In embodiments, thedevice is supplied as putty, pre-loaded in a syringe applicator, andpackaged in a sterile barrier foil pouch or blister tray. Inembodiments, the device is provided sterile, for single use, in avariety of sizes.

The moldable bone graft compositions of the present disclosure may besupplied with, or used in conjunction with, allograft tissue. Thus, inaspects, the moldable bone graft compositions taught herein compriseallograft tissue. In other aspects, a physician may add the allografttissue at the point of care in conjunction with the moldable bone graftcompositions taught herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a posterior view of a bone graft composition according to anembodiment implanted between transverse processes of vertebra.

FIG. 1B is a side view of bone graft compositions according toembodiments disposed between vertebral bodies and on posterior portionsof vertebrae.

FIG. 1C is a side view of a bone graft composition according to anembodiment disposed proximate to a facet joint of a spine.

FIG. 1D is an anterior view of a bone graft composition according to anembodiment disposed on an ilium.

FIG. 1E is an anterior view of bone graft compositions according toembodiments disposed at an iliac crest and an acetabulum.

FIG. 1F is a side view of a bone graft composition according to anembodiment disposed in a radius (which is shown adjacent an ulna).

FIG. 1G is a perspective view of a bone graft composition according toan embodiment disposed in a femur.

FIG. 1H is a side view of bone graft compositions according toembodiments disposed on bones of a foot and at an ankle joint.

FIG. 2A is a perspective view of a bone graft material according to anembodiment.

FIG. 2B is the bone graft material of FIG. 2A implanted into a bone voidin a cranium.

FIG. 3 is an SEM image that illustrates the in vitro testing of amoldable bone graft composition in simulated body fluid at time pointzero and at 1 day and at 7 days. The moldable bone graft compositiondemonstrated apatite layer formation on the bioactive glass surface inas early as 1 day.

FIG. 4 is a histology stain that illustrates surface resorption of thebiphasic mineral utilized in the moldable bone graft compositions taughtherein (top panel) is superior to that of HA-based Actifuse ABX granules(bottom panel). G=granules, NB=new bone.

FIG. 5 is a histology slide of the bone graft composition from a rabbitposterolateral spine fusion study, demonstrating new bone formation froma starting time point 0, to 6 weeks, to 12 weeks.

FIG. 6 is a pair of histology slides of the bone graft composition froma rabbit posterolateral spine fusion study demonstrating bilateralfusion within the same animal characterized by new mature bone formationspanning the transverse processes at 12 weeks.

FIG. 7 is a histology slide of HA-based Actifuse ABX from a rabbitposterolateral spine fusion study demonstrating an absence of new bonespanning the transverse processes at 12 weeks.

FIG. 8 is a histology slide of 45S5 bioactive glass used alone from arabbit posterolateral spine fusion study demonstrating an absence of newbone spanning the transverse processes at 14 weeks.

FIG. 9A illustrates that the moldable bone graft compositions taughtherein lead to Saos-2 cell proliferation that is significantly increasedwhen compared to the control at both 1 and 3 day time points.Proliferation was also increased with respect to 45S5 Bioactive Glass aswell as the Biphasic granule, but only significantly at day 1

FIG. 9B illustrates that the moldable bone graft compositions taughtherein lead to significantly increased cell proliferation in the MG63cell line at 3 days, in two different seeding densities.

FIG. 9C illustrates that in the differentiation assay both MG63 andC2C12 cell lines were cultured with or without the presence ofconditioned media. It was shown that MG63 cells upregulated ALPactivity, a sign of osteoblast differentiation, at 14 and 21 days,although only statistically significantly so at 21 days.

FIG. 9D illustrates that in the differentiation assay both MG63 andC2C12 cell lines were cultured with or without the presence ofconditioned media. It was shown that the C2C12 cell line showedstatistically significant ALP upregulation at 7 days, in comparison toboth the control and the biphasic mineral and an increase compared tocontrol at day 14, but that increase was not significant. ALP levelswere quantified in the cell lysate and normalized to protein levels ineach condition.

FIG. 10 illustrates that bone graft compositions of the disclosuredecreased the colony forming units of all organisms throughout thecourse of the study, satisfying the category 1 acceptance criteria ofUSP 51.

DETAILED DESCRIPTION

Compositions, materials, methods, and kits for bone grafting, includingfor repairing and/or filling a void or gap in a bone or other bonystructure of a patient, are described herein. Also described herein aremethods for preparing such compositions and materials.

Definitions

As used in this specification, the singular forms “a,” “an” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, the term “a material” is intended to mean one or morematerials, or a combination thereof.

As used herein, the term “biocompatible” refers to the ability (e.g., ofa composition or material) to perform with an appropriate host responsein a specific application, or at least to perform without having a toxicor otherwise deleterious effect on a biological system of the host,locally or systemically.

As used herein, the term “osteoconductive” refers to the ability (e.g.,of a composition or material) to passively permit bone growth (e.g.,onto and/or into the material). As such, osteoconduction can becharacterized as a passive process.

A material (e.g., a graft or implant) can be osteoconductive, forexample, because it is configured to passively permit growth of bone ona surface of the material. In another example, a material can beosteoconductive, because it is configured to passively permit growth ofbone into an opening (e.g., a pore) of the material.

As used herein, the term “osteoinductive” refers to the capability(e.g., of a composition or material) to actively stimulate a biologicalresponse which induces bone formation. As such, osteoinduction can becharacterized as an active process.

Osteoinduction can include the formation and/or stimulation ofosteoprogenitor cells, such as osteoprogenitor cells in bodily tissuesurrounding or proximate to a graft or implant.

As used herein, the term “bioactive” refers to the capability (e.g., ofa composition or material) to form a hydroxyapatite (HA) surface layerwhen immersed in simulated body fluid (SBF)

As used herein, the term “osteostimulative” refers to the capability(e.g., of a composition, material, or extract thereof) to enhance oractively stimulate proliferation of osteoblasts and differentiation ofmesenchymal stem cells.

As used herein, the term “anti-bacterial” or “anti-microbial” refers tothe capability (e.g., of a composition, materials, or extract thereof)to inhibit the growth of microorganisms based on methods described inUSP <51>.

As used herein, the term “biodegradable” refers to the capability of amaterial to be degraded, disassembled, and/or digested over time byaction of a biological environment (including the action of livingorganisms, e.g., the patient's body) and/or in response to a change inphysiological pH or temperature. Biodegradable, in the context of ahuman body environment, implies that the material is degraded,disassembled, and/or digested under normal physiological conditions.

As used herein, the terms “resorbable” and “bioresorbable” refers to thecapability of a material to be broken down over a period of time andassimilated into the biological environment. Resorbable andbioresorbable, in the context of a human body environment, implies thatthe material is broken down over a period of time and assimilated intothe body under normal physiological conditions.

As used herein, the term “moldable” refers to the property of beingpliable, able to be compressed, shaped, and manipulated by force ofhand, while maintaining integrity, homogeneity of the composition,physical properties, and performance properties.

As used herein, references to a weight of components of a bone graftcomposition or material described herein, such as the phrase “byweight,” refer to the weight of the applicable component prior to beingadded to or mixed with another different component of the bone graftcomposition. For example, the weight can refer to an initial weight ofthe component measured out before further processing of the componentinto the bone graft composition.

As used herein, the phrase “non-load bearing application” refers to anapplication for repair of a void or gap in a bone or another bonystructure in which the void or gap to be repaired is not intrinsic tothe stability of the bone or bony structure.

A bone graft composition, or material, according to an embodimentfacilitates repair or regeneration of bone at a target repair site. Forexample, in some embodiments, the bone graft composition can beosteoconductive, osteoinductive, bioactive, osteostimulative,antibacterial or any combination thereof. The target repair site can be,for example, a void, gap, or other defect in a bone or other bonystructure in a body of a patient. For example, as described in moredetail below, the bone graft composition facilitates bone growth at atarget repair site in the spine, pelvis, an extremity, the cranium, oranother bone or bony structure in the patient's body. The bone graftcomposition can be implanted or otherwise disposed or molded at thetarget repair site. For example, in some embodiments, the bone graftcomposition can be implanted or disposed at the target repair site in anon-load bearing application.

Bioresorbable Polymers

In embodiments, the bioresorbable polymers utilized in the disclosureare alkylene oxide polymers (AOP).

The alkylene oxide polymers, alternatively referred to as poly(alkyleneoxide)s, are linear or branched-chain polymers (including homopolymers,copolymers, and graft copolymers) that contain ether linkages in theirmain polymer chain structure and are derived from monomers that arevicinal cyclic oxides, or epoxides, of aliphatic olefins, such asethylene and propylene and, to some extent, butylene.

The alkylene oxide polymers of the present invention may have a range ofsuitable molecular weights. Lower molecular weight alkylene oxidepolymers are generally liquids, increasing in viscosity with molecularweight. High molecular weight alkylene oxide polymers can bethermoplastic. The solubilities of alkylene oxide polymers range fromhydrophilic water soluble polymers that are principally derived fromethylene oxide, to hydrophobic, oil-soluble polymers of propylene oxideand butylene oxide.

In embodiments, the polymer carrier comprises a polyethylene glycol or“PEG” polymer, which is an addition polymer of ethylene oxide and water,represented by the formula H(OCH₂CH₂)_(n)OH, in which n represents theaverage number of oxyethylene groups.

The structure of polyethylene glycol can be represented as follows:

In particular aspects, the polymer utilized in the moldable bone graftcompositions is one or more of a bioresorbable polymer comprising apolyalkylene oxide polymer having a molecular weight of about 500-1500grams/mole, a specific gravity of about 1.0-1.3 (at 25° C.), a viscosityof about 10-40 cSt (at 210° C.), and a melting temperature of about35-50° C.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450—80% wt/wt; and 2) USP-NF PEG 400—20% wt/wt. In some aspects, thisproperty range may also be achieved using USP-NF PEG 1000. In anembodiment, the polymer carrier has the following properties, per USPtesting: MW=983, Viscosity=19.0 cST (@ 210° F.), and a Tm=44-46° C.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a range of about 50% to about 99% wt/wt; and 2) USP-NF PEG 400in a range of about 1% to about 50% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a range of about 60% to about 90% wt/wt; and 2) USP-NF PEG 400in a range of about 10% to about 40% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a range of about 70% to about 90% wt/wt; and 2) USP-NF PEG 400in a range of about 10% to about 30% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a range of about 75% to about 85% wt/wt; and 2) USP-NF PEG 400in a range of about 15% to about 25% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a concentration of about 80% wt/wt; and 2) USP-NF PEG 400 in aconcentration of about 20% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a concentration of 80%±5% wt/wt; and 2) USP-NF PEG 400 in aconcentration of 20%±5% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a concentration of 80%±2% wt/wt; and 2) USP-NF PEG 400 in aconcentration of 20%±2% wt/wt.

In embodiments, the polymer carrier is a combination of: 1) USP-NF PEG1450 in a concentration of 80%±1% wt/wt; and 2) USP-NF PEG 400 in aconcentration of 20%±1% wt/wt.

Bioactive Glass

The bioactive glass of the bone graft composition facilitates theregrowth of bone at the target repair site.

In some embodiments, the bioactive glass of the bone graft compositioncan be an osteoconductive agent. The bioactive glass can be disposed on,embedded within, suspended within, and/or otherwise mixed with thealkylene oxide polymer carrier of the bone graft material.

In some embodiments, the bioactive glass can be mixed with the alkyleneoxide polymer carrier such that the bioactive glass is randomlydispersed throughout the alkylene oxide polymer carrier.

For example, the bioactive glass can be mixed with the alkylene oxidepolymer carrier to form a substantially homogenous mixture (e.g., aslurry or dispersion) of carrier and bioactive glass.

In some embodiments, the bioactive glass is disposed on (e.g., coated orsprinkled onto) a surface of the alkylene oxide polymer carrier (e.g.,the carrier matrix in one of a flowable, dried, or sponge-like forms).

The bioactive glass can be any alkali-containing ceramic, glass,glass-ceramic, or crystalline material that facilitates bone formationafter contact with a biological environment.

Suitable bioactive glasses can include 45S5, 58S, S70C30, or acombination of the foregoing bioactive glasses.

Specifically, in some embodiments, the bioactive glass is a 45S5bioglass comprising SiO₂, Na₂O, CaO and P₂O₅. In embodiments the 45S5bioglass has a nominal chemical composition of 45% silicon dioxide(SiO₂) (±2%), 24.5% calcium oxide (CaO) (±2%), 24.5% sodium oxide (Na₂O)(±2%), and 6% phosphorous pentoxide (P₂O₅) (±1%).

The bioactive glass can include trace or minimal amounts of at least oneheavy element, including, but not limited to, arsenic (As), cadmium(Cd), mercury (Hg), lead (Pb), or a combination thereof. For example,the bioactive glass can include As in an amount less than about 3 partsper million (ppm). In another example, the bioactive glass can includeCd in an amount less than about 5 ppm. In yet another example, thebioactive glass can include Hg in an amount less than about 5 ppm. Instill another example, the bioactive glass can include Pb in an amountless than about 30 ppm. Specifically, in some embodiments, the bioactiveglass is a 45S5 bioglass of the composition described above andincluding 3 ppm As, 5 ppm Cd, 5 ppm Hg, and 30 ppm Pb.

The bioactive glass can be in any suitable form. For example, in someembodiments, the bioactive glass is in particulate form. In theparticulate form, the bioactive glass particles are discrete andgenerally not interconnected. As such, the bioactive glass particles,collectively, are generally amorphous. In other words, the bioactiveglass particles, collectively, generally lack an intentional structureor organization. The bioactive glass particles can be generallyirregular in shape. The bioactive glass particles can have a smoothsurface.

The bioactive glass particles can be any suitable size. In someembodiments, at least a portion of the bioactive glass particles arewithin a range of about 1 μm to about 1000 μm, or about 1 μm to about900 μm, or about 1 μm to about 800 μm, or about 1 μm to about 700 μm, orabout 1 μm to about 600 μm, or about 1 μm to about 500 μm, or about 1 μmto about 400 μm, or about 1 μm to about 300 μm, or about 1 μm to about200 μm, or about 1 μm to about 100 μm in size.

In other embodiments, at least a portion of the bioactive glassparticles are within a range of about 100 μm to about 1000 μm, or about100 μm to about 900 μm, or about 100 μm to about 800 μm, or about 100 μmto about 700 μm, or about 100 μm to about 600 μm, or about 100 μm toabout 500 μm, or about 100 μm to about 400 μm, or about 100 μm to about300 μm, or about 100 μm to about 200 μm in size.

In other embodiments, at least a portion of the bioactive glassparticles are within a range of about 200 μm to about 1000 μm, or about200 μm to about 900 μm, or about 200 μm to about 800 μm, or about 200 μmto about 700 μm, or about 200 μm to about 600 μm, or about 200 μm toabout 500 μm, or about 200 μm to about 400 μm, or about 200 μm to about300 μm in size.

In other embodiments, at least a portion of the bioactive glassparticles are within a range of about 300 μm to about 1000 μm, or about300 μm to about 900 μm, or about 300 μm to about 800 μm, or about 300 μmto about 700 μm, or about 300 μm to about 600 μm, or about 300 μm toabout 500 μm, or about 300 μm to about 400 μm in size.

In other embodiments, at least a portion of the bioactive glassparticles are within a range of about 200 μm to about 430 μm, or about200 μm to about 425 μm, or about 200 μm to about 420 μm in size, orabout 210 μm to about 430 μm, or about 210 μm to about 425 μm, or about210 μm to about 420 μm in size.

In other embodiments, at least a portion of the bioactive glassparticles are within a range of about 212 μm to about 420 μm, or about212 μm to about 425 μm in size.

In other embodiments, the bioactive glass particles have an averageparticle size of about 200 μm, about 210 μm, about 220 μm, about 230 μm,about 240 μm, about 250 μm, about 260 μm, about 270 μm, about 280 μm,about 290 μm, about 300 μm, about 310 μm, about 320 μm, about 330 μm,about 340 μm, about 350 μm, about 360 μm, about 370 μm, about 380 μm,about 390 μm, about 400 μm, about 410 μm, about 420 μm, or about 430 μm,inclusive of all ranges and subranges there between.

The bioactive glass can include particles of various sizes; for example,of various sizes within at least one of the foregoing ranges. In someembodiments, the bioactive glass particles are sufficiently large toprevent the particles from leaching out of the alkylene oxide polymercarrier.

In some embodiments, at least 55% of the bioactive glass particles arewithin a range of about 212 μm to about 425 μm in size. In someembodiments, at least 65% of the bioactive glass particles are within arange of about 212 μm to about 425 μm in size. In some embodiments, atleast 75% of the bioactive glass particles are within a range of about212 μm to about 425 μm in size. In some embodiments, at least 85% of thebioactive glass particles are within a range of about 212 μm to about425 μm in size. In some embodiments, at least 90% of the bioactive glassparticles are within a range of about 212 μm to about 425 μm in size. Insome embodiments, at least 95% of the bioactive glass particles arewithin a range of about 212 μm to about 425 μm in size. In someembodiments, 100% of the bioactive glass particles are within a range ofabout 212 μm to about 425 μm in size.

In some embodiments, about <2% of the bioactive glass particles have aparticle size >425 μm, about 92% of the bioactive glass particles have aparticle size from 212-425 μm, and about <7% of the bioactive glassparticles have a particle size <212 μm.

Any suitable method of measuring the bioactive glass particle size maybe used. For example, the bioactive glass particles can be sieved usingASTM sieves according to ASTM E 11-70 (1995) method. When using such amethod, for example, particles (or granules) retained between 40 and 70mesh can be used in the moldable bone graft composition. Becauseparticles screened within a certain range may contain a small amount ofsmaller particles due to screen blinding, a precision screen may be usedto determine the amount of particles within the desired particle sizerange.

Calcium Phosphate Particles

The calcium phosphate of the moldable bone graft composition alsofacilitates the regrowth of bone at the target repair site.

In some embodiments, the calcium phosphate of the moldable bone graftcomposition is an osteoconductive agent. The calcium phosphate isdisposed on, embedded within, suspended within, and/or otherwise mixedwith the alkylene oxide polymer carrier.

In some embodiments, the calcium phosphate can be mixed with thealkylene oxide polymer carrier such that the calcium phosphate israndomly dispersed throughout the carrier.

For example, the calcium phosphate can be mixed with the alkylene oxidepolymer carrier to form a substantially homogenous mixture (e.g., aslurry or dispersion) of carrier and calcium phosphate. In anotherexample, the calcium phosphate can be mixed with the alkylene oxidepolymer carrier and the bioactive glass.

The calcium phosphate can include any suitable calcium phosphate ormineral thereof, including, but not limited to, hydroxyapatite(sometimes referred to as hydroxylapatite; also referred to herein as“HA”), tricalcium phosphate (also referred to herein as “TCP”),β-tricalcium phosphate (also referred to herein as β-TCP, or beta-TCP)or a combination of the foregoing.

In some embodiments, the calcium phosphate is biphasic and includestricalcium phosphate and hydroxyapatite. For example, the calciumphosphate can be biphasic and include HA and β-TCP. In one aspect, themoldable bone graft compositions taught herein comprise biphasicHA/β-TCP particles that contain about 20-60% hydroxyapatite and about40-80% β-tricalcium phosphate. In some aspects, the moldable bone graftcompositions taught herein comprise biphasic HA/β-TCP particles thatcontain about 60% hydroxyapatite and about 40% β-tricalcium phosphate.

The calcium phosphate can be in any suitable form. For example, thecalcium phosphate can be in particulate or granular form. The calciumphosphate can be of any suitable size. For example, in some embodiments,the calcium phosphate includes mineral particles within the range ofabout 1 mm to about 2 mm in size. In some embodiments, the calciumphosphate includes mineral particles within the range of about 1 mm toabout 2.5 mm. In some embodiments, the calcium phosphate includesmineral particles within the range of about 0.5 mm to about 2 mm insize. In some embodiments, the calcium phosphate includes mineralparticles within the range of about 0.5 mm to about 2.5 mm.

In some embodiments, at least a portion of the calcium phosphateparticles are within a range of about 500 μm to about 3000 μm, or about500 μm to about 2500 μm, or about 500 μm to about 2000 μm in size.

In some embodiments, at least a portion of the calcium phosphateparticles are within a range of about 1000 μm to about 3000 μm, or about1000 μm to about 2500 μm, or about 1000 μm to about 2000 μm in size.

In some embodiments, about 10-99% of the calcium phosphate particleshave a granule size of about 1000-2000 μm. In some embodiments, about20-99% of the calcium phosphate particles have a particle size of about1000-2000 μm. In some embodiments, about 30-99% of the calcium phosphateparticles have a particle size of about 1000-2000 μm. In someembodiments, about 40-99% of the calcium phosphate particles have aparticle size of about 1000-2000 μm. In some embodiments, about 50-99%of the calcium phosphate particles have a particle size of about1000-2000 μm. In some embodiments, about 60-99% of the calcium phosphateparticles have a particle size of about 1000-2000 μm. In someembodiments, about 70-99% of the calcium phosphate particles have aparticle size of about 1000-2000 μm. In some embodiments, about 80-99%of the calcium phosphate particles have a particle size of about1000-2000 μm. In some embodiments about 90%, or more, of the calciumphosphate particles have a particle size of about 1000-2000 μm.

In some embodiments, about 10-70% of the calcium phosphate particleshave a particle size of about 425-1000 μm. In some embodiments, about10-50% of the calcium phosphate particles have a particle size of about710-1000 μm. In some embodiments, about 1-30% of the calcium phosphateparticles have a particle size of about 425-710 μm.

In some embodiments, about <1% of the calcium phosphate particles have aparticle size >2000 μm, about 63% of the calcium phosphate particleshave a particle size from 1000-2000 μm, about 27% of the calciumphosphate particles have a particle size from 710-1000 μm, and about 9%of the calcium phosphate particles have a particle size of 425-710 μm.

Weight Ratios of Bone Graft Compositions

Moldable bone graft compositions of various weight ratios of alkyleneoxide polymer, bioactive glass, and calcium phosphate are contemplated.

In some embodiments, a moldable bone graft composition includes about40% to about 80% by weight of an alkylene oxide polymer carrier, about10% to about 50% by weight of biphasic calcium phosphate particles, andabout 1% to about 40% by weight of a bioactive glass, wherein thecalcium phosphate and bioactive glass together comprise about 20% toabout 60% by weight of the bone graft composition.

In some embodiments, a moldable bone graft composition includes about50% to about 70% by weight of an alkylene oxide polymer carrier, about25% to about 40% by weight of a biphasic calcium phosphate particles,and about 1% to about 15% by weight of a bioactive glass, wherein thecalcium phosphate and bioactive glass together comprise about 30% toabout 50% by weight of the bone graft composition.

In some embodiments, a moldable bone graft composition includes about55% to about 65% by weight of an alkylene oxide polymer carrier, about25% to about 35% by weight of biphasic calcium phosphate particles, andabout 5% to about 10% by weight of a bioactive glass.

In some embodiments, a moldable bone graft composition includes 60%±30%by weight of an alkylene oxide polymer carrier, 32%±30% by weight ofbiphasic calcium phosphate particles, and 8%+30/−7% by weight of abioactive glass.

In some embodiments, a moldable bone graft composition includes 60%±20%by weight of an alkylene oxide polymer carrier, 32%±20% by weight ofbiphasic calcium phosphate particles, and 8%+20/−7% by weight of abioactive glass.

In some embodiments, a moldable bone graft composition includes 60%±10%by weight of an alkylene oxide polymer carrier, 32%±10% by weight ofbiphasic calcium phosphate particles, and 8%+10/−7% by weight of abioactive glass.

In some embodiments, a moldable bone graft composition includes 60%±5%by weight of an alkylene oxide polymer carrier, 32%±5% by weight ofbiphasic calcium phosphate particles, and 8%±5% by weight of a bioactiveglass.

In some embodiments, a moldable bone graft composition includes 60%±1%by weight of an alkylene oxide polymer carrier, 32%±1% by weight ofbiphasic calcium phosphate particles, and 8%±1% by weight of a bioactiveglass.

In some embodiments, a moldable bone graft composition includes about60% by weight of an alkylene oxide polymer carrier, about 32% by weightof biphasic calcium phosphate particles, and about 8% by weight of abioactive glass.

In one embodiment, the moldable bone graft composition comprises about60% by weight of an alkylene oxide polymer carrier, about 32% by weightof biphasic calcium phosphate particles, and about 8% by weight of abioactive glass, and each of the components is composed of the elementsas set forth below in Table 1 at the indicated percentages wt/wt.

TABLE 1 PEG PEG >2000 1000-2000 710-1000 425-710 >425 212-425 <212 1450400 microns microns microns microns microns microns microns Polymer 48%12% Carrier (60%) Biphasic <1% 63% 27% 9% Calcium Phosphate (32%)Bioactive Glass <2% 92% <7% (8%)

In other embodiments, the moldable bone graft components set forth abovein Table 1 have a range of ±30% of each component, or a range of ±20% ofeach component, or a range of ±10% of each component, or a range of ±5%of each component, or a range of ±1% of each component.

In the foregoing examples, the alkylene oxide polymer, bioactive glass,and calcium phosphate can be any alkylene oxide polymer, bioactiveglass, and calcium phosphate, respectively, described herein. Forexample, the calcium phosphate can be biphasic and include about 60% HAand about 40% β-TCP.

In embodiments, the moldable bone graft composition is, prior toimplantation into the patient's body, free of additional componentsincluding, but not limited to, bone or forms thereof (e.g., boneparticles, bone powder, demineralized bone matrix), cells, tissueparticles, blood products, calcium phosphate, rubber, gelatin, bonemorphogenetic proteins, growth factors, anti-inflammatory agents, drugs,and radiopaque particles.

Target Repair Site Applications

As noted above, a moldable bone graft composition according to anembodiment can be used at various target repair sites within a body of apatient to facilitate bone growth therein.

In some embodiments, the moldable bone graft composition is used at atarget repair site in the patient's spine. For example, as shown in FIG.1A, a moldable bone graft composition 10 can be disposed in an openingbetween a transverse process of a first vertebra and a transverseprocess of a second vertebra. In this manner, the moldable bone graftcomposition can facilitate growth of a bony bridge between thetransverse processes of the first and second vertebrae, such as toachieve posterolateral spinal fusion.

In another example, as shown in FIG. 1B, a moldable bone graftcomposition 20 can be disposed in a void or opening between a body of afirst vertebra and a body of a second vertebra different than the firstvertebra. In this manner, for example, the moldable bone graftcomposition can facilitate growth of bone between the body of the firstvertebra and the body of the second vertebra to achieve interbody fusionof the vertebrae. Referring again to FIG. 1B, in some embodiments, aplurality of moldable bone graft composition implants 22 can bepositioned adjacent a posterior portion of the spine, for example, tofacilitate growth of a bony bridge between adjacent vertebrae. In thismanner, the plurality of moldable bone graft composition implants 22 canfacilitate fusion of the adjacent vertebrae. In some embodiments, suchas in a spinal fusion procedures, the moldable bone graft composition isused in conjunction with a mechanical support (e.g., a plurality ofscrews and/or rods, as shown in FIG. 1B).

In still another example, referring to FIG. 1C, a moldable bone graftcomposition 30 can be implantable in, or proximate to, a facet joint ofadjacent vertebrae to facilitate growth of bone at the facet joint.

In some embodiments, a moldable bone graft composition is used at atarget repair site in the patient's pelvis. For example, as shown inFIG. 1D, a moldable bone graft composition 40 can be disposed in anopening in the patient's ilium.

In some embodiments, a moldable bone graft composition is disposed in,or at a target repair site, at a different portion of the pelvis, suchas, for example, the iliac crest (e.g., moldable bone graft composition50 shown in FIG. 1E), acetabulum (e.g., moldable bone graft composition52 shown in FIG. 1E), ischium, or pubis.

In some embodiments, a moldable bone graft composition is used at atarget repair site in a bone of an extremity of the patient. Forexample, a moldable bone graft composition can be disposed in an openingin the radius (e.g., moldable bone graft composition 60 in FIG. 1F),ulna, humerus, tibia, fibula, femur (e.g., moldable bone graftcomposition 70 in FIG. 1G), or other bone of an extremity.

In another example, the moldable bone graft composition can beconfigured to be disposed in an opening in a knee joint. In yet anotherexample, referring to FIG. 1H, a moldable bone graft composition isdisposed in an opening in a bone of the patient's foot. For example, insome embodiments, the moldable bone graft composition is disposed in anopening of a calcaneus (i.e., heel bone) (e.g., moldable bone graftcomposition 80), navicular (e.g., moldable bone graft composition 82),talus, cuboid, or cuneiform bone of the foot. In another example,referring to FIG. 1H, a moldable bone graft composition can be in theform of an implant 84 disposed at a target repair site in, or proximateto, an ankle joint, i.e., between the tibia and the talus.

In some embodiments, referring to FIGS. 2A-2B, the moldable bone graftcomposition can be in the form of an implant 100 in or at a targetrepair site in a patient's cranium to facilitate growth of bone therein.Although specific examples of suitable target repair sites have beenillustrated and described, in other embodiments, the moldable bone graftcomposition can be configured to be implanted into or at a target repairsite in a different bone or bony structure of the patient's body.

Moldable Bone Graft Composition Kits

A moldable bone graft material kit, according to an embodiment, includesat least a bioresorbable polymer carrier, such as an alkylene oxidepolymer, and bioactive glass (e.g., in the form of particles), andcalcium phosphate particles.

In one embodiment, the moldable bone graft composition is supplied as animplant preloaded into a syringe. The implant comprises thebioresorbable polymer carrier and bioactive glass.

In one embodiment, the moldable bone graft composition kits comprise abone graft syringe assembly for delivering the bone graft material. Thebone graft syringe assembly comprises: 1) a syringe barrel having aproximal end, a distal end, and an inner chamber adapted for receivingthe moldable bone graft composition, the inner chamber having a proximalopening and a distal opening, and 2) a plunger adapted for expelling themoldable bone graft material through the distal opening of the innerchamber, with the plunger slidably received within the inner chamberthrough the proximal opening.

Methods of Making the Present Moldable Bone Graft Compositions

A method of making a bone graft material according to an embodiment isdescribed herein. The implant is sold already mixed supplied in asyringe.

In one embodiment, the polymer carrier is melted and the bioglass andmineral components are added. The composite is cooled, and the bulkmaterial is hand molded into individual implants.

In certain aspects, these individual implants are loaded into a syringeand sold to a consumer as a preloaded syringe.

Methods of Using the Present Moldable Bone Graft Compositions

A bone graft procedure, according to an embodiment, includes a methodfor implanting a moldable bone graft material or composition (includingany moldable bone graft material or composition described herein) at atarget repair site within a body of a patient.

The bone graft procedure optionally includes preparing the target repairsite of the bone or bony structure within the patient's body to receivethe bone graft material. Preparation of the target repair site caninclude cleansing the site to remove foreign materials, loose bonefragments or powder, or other potentially harmful materials. In someprocedures, preparation of the target repair site includes re-shapingthe site, for example, by removing a portion of the perimeter of thesite so that the site has a desired shape. In other procedures,preparation of the target repair site includes decortication to thelevel of bleeding bone.

The bone graft procedure optionally includes shaping the moldable bonegraft material for placement at the target repair site. For example, thephysician can manually manipulate (e.g., squeeze, pinch, stretch, etc.)the moldable bone graft material. In some embodiments, shaping the bonegraft material includes forming the bone graft material into a desiredshape.

The bone graft procedure includes positioning the bone graft material atthe target repair site. In some embodiments, positioning the bone graftmaterial includes injecting the bone graft material in a flowable stateinto the target repair site. For example, the bone graft material can bein the form of a slurry, foam, paste, solution, or the like, which isinjected into the target repair site via a syringe, or elongated tube,such as in minimally invasive surgery (MIS).

Optionally, at the physician's discretion, the bone graft procedureincludes wetting the bone graft material with a suitable solution beforeor after positioning the bone graft material at the target repair site.In some embodiments, the bone graft material is wetted with a fluid fromthe patient's body. For example, blood or plasma from the patient's bodycan be disposed on or permitted to flow to the bone graft material.

At the physician's discretion, the bone graft procedure includes mixingthe bone graft material with autologous bone, allograft, or a mixture ofthe two.

In one embodiment, the moldable bone graft composition is supplied in ahomogeneous and “ready to use” fashion. In aspects, this “ready to use”fashion is embodied as a moldable bone graft composition preloaded intoa syringe. In this embodiment, the surgeon only has to eject thecomposition from the syringe, knead it with manual force (because in anaspect the composition starts as a cylindrical plug loaded into thesyringe), then mold the composition to the desired shape, and apply thecomposition to the target repair site.

The bone graft procedure optionally includes closing an aperture in thepatient's body that provided access to the target repair site. Forexample, a skin flap can be repositioned over the implanted bone graftmaterial. In some embodiments, sutures, staples, or another closuremechanism are used to help close the aperture in the patient's body. Thepatient can be monitored for symptoms of complication (e.g., infection,rejection of the bone graft material), as well as for regrowth of boneat the target repair site.

Specific examples of moldable bone graft compositions are now described.

EXAMPLES Example 1—Moldable Bone Graft Composition

A synthetic bone graft composition, comprising: (1) resorbable alkyleneoxide polymer (AOP) carrier, (2) biphasic granulate (HA/β-TCP, 60:40),and (3) 45S5 bioactive glass, in a single homogenous and moldableimplant, was prepared.

The moldable bone graft composition comprised the components aspreviously set forth in Table 1.

The moldable bone graft composition was found to provide optimalintra-operative handling, sustained bioactivity, and a resorptionprofile that allows gradual and consistent defect remodeling consistentwith the host remodeling response.

The utilized particle size range of the bioactive glass component(212-425 μm) has demonstrated advantages over the more common broaderranges featured in commercial bioactive glass products.

It was discovered that a narrow particle size distribution will yield amore controlled rate of ion dissolution and surface reactivity,producing a more consistent rate of bone bonding and proliferationthroughout the defect site.

Smaller particles (<210 μm) can degrade quickly, causing a transientinflammatory response that may impede the up-regulation ofosteoprogenitor cells. Larger particles (>420 μm) may not fully degrade,leaving unreacted glass particles at the defect site that can delayosteoconduction and remodeling. In addition, 45S5 bioactive glass hasbeen shown to be antimicrobial, bioactive, and osteostimulatory insimulated physiological environments.

The utilized biphasic mineral granulate provides distinct advantagesover HA and β-TCP based materials, in terms of implant resorption andremodeling.

Hydroxyapatite (HA) is largely insoluble with bone bonding limited tothe surface. Despite compositional modifications such as “silicatesubstitution,” the potential for limited resorption and remodelingremains, which may leave the defect site susceptible to focusedmechanical stress. See, e.g., Vaccaro AR. The Role of theOsteoconductive Scaffold in Synthetic Bone Graft. Orthopedics 2002,25(5):571-78; and also Szpalski M, Gunzburg R. Applications ofPhosphate-Based Cancellous Bone Void Fillers in Trauma Surgery.Orthopedics 2002, 25(5):601-09.

Beta tricalcium phosphate (β-TCP) is similar in composition to amorphousbone precursors and readily undergoes remodeling, stimulated by thematerial's calcium phosphate-rich surface layers. However, β-TCP canpotentially resorb faster than the rate of new bone formation, resultingin non-mineralized fibrous tissue at the implant site. Despiteenhancements to β-TCP, as with Vitoss Scaffold Foam Pack (Orthovita),resorption of β-TCP has been reported to be unpredictable in biologicalenvironments. See, e.g., Vaccaro AR. The Role of the OsteoconductiveScaffold in Synthetic Bone Graft. Orthopedics 2002, 25(5):571-78;Szpalski M, Gunzburg R. Applications of Phosphate-Based Cancellous BoneVoid Fillers in Trauma Surgery. Orthopedics 2002, 25(5):601-09; Hing KA, Wilson L F, Revell P A, Buckland T. Comparative performance of threebone graft substitutes. Spine J 2007, 7(4):475-90; and also Betz R R.Limitations of Autograft and Allograft: New Synthetic Solutions.Orthopedics 2002, 25(5):561-70.

To address the limitations of these biomaterials, the presently utilizedbiphasic calcium phosphate materials combine the long term stability ofHA with the solubility of β-TCP, which results in an osteoconductivematerial with a gradual and controlled resorption profile optimal forbone defect remodeling.

Thus, the present biphasic HA/β-TCP calcium phosphate particles, in a60:40 ratio of HA to β-TCP, were unexpectedly superior to HA or β-TCPparticles utilized in isolation. The combination of these particles, inthe specified ratio and at the specified particle size, yields superiorresults.

Example 2—Demonstration of Bioactivity of Bioactive Glass Component

The bioactive glass component of the moldable bone graft compositionutilized in Example 1 undergoes a unique surface modification within thephysiological environment that allows for direct bonding withsurrounding bone. Following implantation, an exchange of biologicallyactive ions produces a bioactive hydroxy carbonate apatite (HCA) layerto which bone can readily bond to. These surface reactions are followedby the proliferation and differentiation of bone related cells on theapatite matrix as part of the normal healing process. For example, themoldable bone graft composition taught herein demonstrated apatite layerformation in a simulated body fluid (SBF) on the bioactive glass surfacein as early as 1 day (FIG. 3 ).

We have determined that particle size distribution of bioactive glass isa critical factor to bone bonding performance. The particle size rangeof the bioactive glass (212-425 μm) utilized in the present experimenthas demonstrated advantages over the more commonly utilized 90-710 μmrange (Novabone), including higher rates of new bone formation andmaterial remodeling at the defect site. See, Yang S S. Compositions andMethods to Repair Osseous Defects. U.S. Pat. No. 6,228,386 (2001),incorporated by reference herein. Generally, a narrow particle sizedistribution will yield a more controlled rate of ion dissolution andsurface reactivity, producing a more consistent rate of bone bonding andproliferation throughout the defect site. Smaller particles (<210 μm)can degrade quickly, causing a transient inflammatory response that mayimpede the up-regulation of osteoprogenitor cells. Larger particles(>420 μm) may not fully degrade, leaving unreacted glass particles atthe defect site that can delay osteoconduction and remodeling. See,Schepers E J G, Oucheyne P., Bioactive glass particles of narrow sizerange for the treatment of oral bone defects: a 1-24 month experimentwith several materials and particle sizes and size ranges. J Oral Rehab1997, 24:171-181.

Example 3—Demonstration of Biphasic Remodeling

Hydroxyapatite (HA) is similar in composition to human bone. However,the material is largely insoluble, with bone bonding limited to thesurface. Despite compositional modifications such as “silicatesubstitution” as with Actifuse ABX (Apatech/Baxter), the potential forlimited resorption and remodeling remains, which may leave the defectsite susceptible to focused mechanical stress. See, e.g., Vaccaro A R.The Role of the Osteoconductive Scaffold in Synthetic Bone Graft.Orthopedics 2002, 25(5):571-78; Szpalski M, Gunzburg R. Applications ofPhosphate-Based Cancellous Bone Void fillers in Trauma Surgery.Orthopedics 2002, 25(5):601-09.

Beta tricalcium phosphate (β-TCP) is similar in composition to amorphousbone precursors and readily undergoes remodeling, stimulated by thematerial's calcium phosphate rich surface layers. See, e.g., Szpalski M,Gunzburg R. Applications of Phosphate-Based Cancellous Bone Void fillersin Trauma Surgery. Orthopedics 2002, 25(5):601-09; Hing K A. Wilson Lf,Revell P A, Buckland T. Comparative performance of three bone graftsubstitutes. Spine J 2007, 7(4):475-90. However, β-TCP can potentiallyresorb faster than the rate of new bone formation, resulting innon-mineralized fibrous tissue at the implant site. Id. Despiteenhancements to β-TCP, as with Vitoss Scaffold Foam Pack (Orthovita),resorption of β-TCP has been reported to be unpredictable in biologicalenvironments. Id., and see also, Betz R R. Limitations of Autograft andAllograft: New Synthetic Solutions. Orthopedics 2002, 25(5): 561-70.

To address the limitations of these biomaterials, the present biphasiccalcium phosphate materials, utilized in the moldable bone graftcompositions, combine the long term stability of HA with the solubilityof β-TCP, resulting in an osteoconductive material with a gradual andcontrolled resorption profile optimal for bone defect remodeling.

Specifically, biphasic mineral formulated in a 60:40 (HA:β-TCP) ratio,as featured with the present moldable bone graft compositions, hasdemonstrated advantageous bone remodeling properties in both benchtesting and in clinically relevant animal studies. See, Daculsi G,Laboux O, Malard O, Weiss P. Current state of the art of biphasiccalcium phosphate bioceramics. J Mater Sci. Mater Med 2003, 14:195-200;Fellah B H, Gauthier O, Weiss P, Chappard D, Layrolle P. Osteogenicityof biphasic calcium phosphate ceramics & bone autograft in a goat model.Biomoterials 2008, 29:1177-1188; Legeros R Z, Lin S, Rohanizadeh R, Mijares D, Legeros J P. Biphasic calcium phosphate bioceramics:preparation, properties & applications. J Mater Sci Mater Med 2003,14:201-09. Following implantation, dissolution of biphasic mineralproduces a direct bonding interface with host bone through the releaseof calcium and phosphate ions and subsequent formation of a surfaceapatite layer similar to bone mineral. Id.

In addition, the structural microporosity and macroporosity of thepresently utilized biphasic granules (1-2 mm) are in the optimal rangesneeded to allow penetration of biological fluids (>10 μm) and to supportosteoconductivity (>100 μm), providing a more sustained remodelingresponse at the defect site. Clinical studies have shown efficacy ofmicroporous and macroporous biphasic calcium phosphate in thereconstruction of large bony defects, including in posterior spinalfusion procedures, and suggest biphasic mineral is a safe alternative toautografts and allografts. See, Garrido C A, Lobo S E, Turibio F M,Legeros R Z. Biphasic calcium phosphate bioceramics for orthopaedicreconstructions: clinical outcomes. lntl Biomoter 2011, 2011:129727; XieY, Chopin D, Morin C, Hardouin P, Zhu Z, Tang J, Lu J. Evaluation of theosteogenesis and biodegradation of porous biphasic ceramic in the humanspine. Biomoteriols 2006, 27(13):2761-7; Betz R R. Limitations ofAutograft and Allograft: New Synthetic Solutions. Orthopedics 2002,25(5):561-70.

Thus, the biphasic mineral granulate utilized in the present disclosureprovides distinct advantages over HA-based materials such as ActifuseABX in terms of implant resorption and remodeling. FIG. 4 visuallydemonstrates the gradual resorption of the present biphasic mineralcompared to Actifuse ABX in a rabbit posterolateral spine fusion (PLF)study. See, Soden S D, Schimandle J H, Hutton H C. An ExperimentalIntertransverse Process Spinal Fusion Model: Radiographic, Histologic &Biomechanical Healing Characteristics. Spine. 1995, 20:412-20.

The gradual resorption rate, porosity, and microstructure of thebiphasic mineral utilized in the present moldable bone graftcompositions result in a stable scaffold that allows sustainedosteoconductivity during the healing process.

Example 4—Demonstration of Synergistic Fusion Effect

The presently utilized combination of 45S5 bioactive glass and 60:40biphasic mineral (HA:β-TCP) provide a synergistic composite bone graftoptimized for sustained bioactivity and remodeling in posterolateralspine fusion procedures.

FIG. 5 demonstrates the healing mechanism of action as follows: Afterimplantation, the polymer carrier rapidly resorbs into surroundingtissues and the bioactive glass particles elicit a versatilebiostimulative response throughout the matrix of biphasic granules. Thisresponse encourages the adhesion, proliferation and differentiation ofbone healing cells onto the newly formed surface apatite layer, andfacilitates a uniform progression of these processes to the biphasicgranule matrix. The biphasic matrix resorbs in tandem with the hostremodeling process to facilitate maturation of the fusion sitethroughout the healing process.

Thus, the representative performance of the presently taught moldablebone graft compositions in a rabbit PLF model is depicted, wherebridging bone was consistently observed spanning transverse processes by12 weeks in vivo, with new bone in direct apposition to, and dispersedbetween, the biphasic granules. See, Example 7, setting forth fullstudy. See also, Boden S D, Schimandle J H, Hutton H C. An ExperimentalIntertransverse Process Spinal Fusion Model: Radiographic, Histologic &Biomechanical Healing Characteristics. Spine. 1995, 20:412-20.

Example 5—In Vitro Bioactivity Test

The in vitro bioactivity of the present moldable bone graft compositionswas evaluated using the currently accepted definition and endpoint ofhydroxyapatite (HA) formation and deposition on the surfaces of glassand ceramic materials when immersed in simulated body fluid (SBF),according to International Standard ISO 23317, Implants for Surgery—Invitro evaluation for apatite-forming ability of implant materials.

Test samples included the moldable bone graft composition of the presentdisclosure comprising 45S5 bioactive glass and biphasic mineral HA/β-TCPgranules, biphasic granules extracted from the finished device, 45S5bioactive glass raw particles used in the fabrication of the finisheddevice, and a commercially available moldable bone graft materialcomprising silicate-substituted hydroxyapatite (HA) granules (1-2 mm)suspended in a resorbable polymer carrier.

A non-apatite forming glass, composition in mol %: 70 SiO2, 15 Na2O, 15CaO, formed into 10 mm diameter disks was used as a control as derivedfrom Annex B from ISO/FDIS 23317:2007 (E).

The moldable bone graft composition of the present disclosure, as wellas the comparative material, were thoroughly mixed by hand, shaped intoa 2.5 cc (3.75 gram) ball, and placed into SBF. Samples each weighing0.3-0.5 grams were immersed in 100 ml of simulated body fluid (SBF) at37° C. for 1, 7, 14, and 28 days and evaluated by X-ray diffraction(XRD), and for pH and weight changes at each time point. SEM images weretaken of all sample sets for comparison.

The polymer carrier dissolved in the SBF similar to how it would in thebody. All experiments were run in triplicate.

X-ray diffraction (XRD) was performed on 45S5 bioactive glass rawparticles and the non-apatite forming glass disks using a PanalyticalX'Pert Multi-Purpose Diffractometer scanning between 10 and 80° 20 at arate of 1°/minute. XRD was not performed on the biphasic granulesextracted from the finished device, the finished moldable bone graftcomposition of the present disclosure, or the comparativesilicate-substituted HA material, because all these materials contain asignificant fraction of HA as the base material, which would makeidentifying a new HA surface formed by the SBF solutionindistinguishable from the parent materials.

No crystalline peaks were identified for the non-apatite forming glasscontrol, before or after immersion in SBF, verifying that HA did notspontaneously precipitate on all materials.

The XRD pattern for the 45S5 raw particles had no evidence ofcrystalline peaks for the unreacted glass, while the 1, 7, 14, and 28day SBF samples did form a crystalline surface layer, and the majorpeaks (around ˜26° &32°) in the patterns corresponded to those of a HA,Ca10(PO4)6(OH)2 (JCPSD 72-1243), indicating the presence of HA on thesurface of the 45S5 raw particles.

Scanning electron microscopy (Hitachi S-4700 SEM) was performed onsamples that were unreacted and samples that had been immersed in SBFfor 1, 7, 14, and 28 days at 37° C. The non-apatite forming glass didnot precipitate any HA on the surface, verifying that the SBF was notspontaneously precipitating HA crystals on free surfaces.

The 45S5 raw particles did have a nanocrystalline HA surface presentafter 1, 7, 14, and 28 days in SBF confirming the results from the XRD.There was no evidence of HA crystals on the biphasic granules or thesilicate-substituted HA material when compared to the unreactedsurfaces. The biphasic granules extracted from the finished device didnot precipitate an identifiable HA layer even in the presence ofbioactive glass particles. This is not surprising since the HAprecipitation on a bioactive material is a surface reaction that doesnot translate to other materials or surfaces even in the vicinity of thebioactive material.

This observation confirms that the combination of 45S5 bioactive glasscombined with biphasic HA/β-TCP granules in a composite materialprovides a biological enhancement over the biphasic granules alone, viathe bioactive nature of the 45S5 bioactive glass.

Example 6—Femoral Defect Animal Study

The aforementioned moldable bone graft composition set forth in Example1 was utilized in a femoral defect animal study.

The moldable bone graft composition of the present disclosure wasevaluated following implantation into distal femoral defects ofskeletally mature New Zealand white rabbits. The objective of this studywas to evaluate the in vivo response of the bone graft of the presentdisclosure, in comparison to a commercially available bone graftmaterial comprising silicate-substituted hydroxyapatite granulessuspended in a resorbable polymer carrier, when implanted in acritical-sized cancellous bone defect.

The animal model chosen provided bilateral cancellous defects (6 mm×10mm) in the distal femur in adult rabbits that have been reported to becritical. The test groups were comparatively evaluated for hostresponse, new bone formation, and implant resorption within the healingdefects using radiographic, microCT, and histologic analyses at timepoints of 1 day, 6 weeks, and 12 weeks.

A total of 11 animals were implanted with the moldable bone graftcomposition of the present disclosure in one femur and the comparativematerial in the contralateral femur. One animal was sacrificed after 1day following surgery, four animals after 6 weeks, and six animals after12 weeks. Following sacrifice, the implant sites were evaluated andcompared for the healing response using radiographic, microCT, andhistological endpoints.

Animals were acclimated for at least seven days prior to surgery.Surgery was performed following standard an aseptic technique undergeneral anesthesia as is understood in the art. A lateral incision,approximately 1.5 centimeters long, was made and the soft-tissuesoverlying the lateral femoral condyle dissected. A 6.0 mm drill bit wasused to drill through the cortex to a depth of 10 mm under constantsaline irrigation. The bone was removed, and a syringe of saline wasused to wash out any remaining bone debris. The bone graft material ofthe present disclosure was hand-packed into the defect to the level ofthe original cortex using approximately 0.3 cc of material. Fascia andskin were closed in the routine manner consistent with good surgicalpractice. This surgical procedure was then conducted on thecontralateral limb using the comparative material. Post-operative careof the animals was performed in accordance with good husbandry practicesas understood in the art.

No complications were observed in either test group over the course ofthe study. Gross observations of the implant sites demonstrated healthytissue absent of adverse inflammatory reactions regardless of test groupor time point. Radiographic analysis indicated no adverse reactions anda normal progression in healing over time in both groups.

MicroCT scans supported the radiographic observations, demonstrating noadverse reactions and a similar osteoconductive healing response in bothgroups, with a progression of new bone formation and implant resorptionobserved over time. The 6 week microCT scans showed host integration andnew bone formation originating from the defect margins in both groups.The 12 week scans showed a progression of host integration and defectremodeling from the 6 week time point, with new bone formationthroughout the implant and defect site in both groups. New boneformation was apparent in direct apposition to and bridging betweenimplant granules.

There was a pronounced change in granular surface appearance in thebiphasic granules of the present disclosure's compositions that was lessapparent in the silicate-substituted hydroxyapatite comparativematerial, indicating the more optimal resorption and remodeling responseachievable with a moldable bone graft composition according to thepresent disclosure.

Histopathology analysis of the defect sites indicated no adversereactions and a similar osteoconductive healing response in both groups,characterized by a progression of new bone formation and implantresorption over time. The 1 day histology images showed the defectmargins and presence of the implant materials with no adverse reactions.The 6 week histology images showed host integration and new boneformation originating from the defect margins in both groups with aprogression of host integration across defect sites at 12 weeks. Newbone formation was apparent in direct apposition to and bridging betweenindividual granules in both groups.

The bioactive glass component of the bone graft of the presentdisclosure was largely resorbed at 6 weeks and replaced by mature hostbone at 12 weeks. The biphasic granule component of the presentdisclosure demonstrated a loss of distinction at the new bone interfacethat was not observed with the silicate-substituted hydroxyapatitematerial. Overall, the moldable bone graft composition of the presentdisclosure demonstrated a consistent progression from woven to maturelamellar bone, with the development of marrow spaces throughout thedefect over time that was not as prevalent in the comparative material.

These observations indicate a more optimal resorption and remodelingresponse in the moldable bone graft compositions of the presentdisclosure, as compared to the silicate-substituted hydroxyapatitematerial, likely due to the combination of bioactive glass and biphasicmineral granulate.

Example 7—Posterolateral Spine Fusion Animal Study

The aforementioned moldable bone graft composition set forth in Example1 was utilized in a posterolateral spine fusion rabbit model.

The moldable bone graft compositions taught herein demonstrated greaterfusion rates than autograft in these experiments.

The results indicate that the standalone implant composed of themoldable bone graft composition is a viable alternative to usingautograft in PLF procedures.

The use of the disclosed moldable bone graft compositions, in place ofautograft in posterolateral spine fusion procedures, can reduce: surgerytime, intraoperative complications, and comorbidities associated withharvesting autograft.

The moldable bone graft composition of the present disclosure wasevaluated following implantation into posterolateral spine defect ofskeletally mature New Zealand white rabbits. A commercially available,moldable bone graft material comprising silicate-substitutedhydroxyapatite granules suspended in a resorbable polymer carrier wasalso evaluated in the study for comparison.

A total of 23 animals were implanted with the bone graft of the presentdisclosure and an additional 23 implanted with the comparative material.One animal was sacrificed after 1 day following surgery, six animalsafter 6 weeks, and ten animals after 12 weeks. Following sacrifice, theimplant sites were evaluated and compared for biocompatibility,osteoconductive healing response and fusion using radiographic, microCT,manual palpation, biomechanical and histological endpoints.

The surgical approach to the spine was identical in all rabbits. Adorsal midline skin incision, approximately 15 centimeters long, wasmade from L1 to the sacrum, and then the fascia and muscle were incisedover the L5-L6 transverse processes (TPs). The TPs were thendecorticated with a high-speed burr. Approximately 2.5-3.0 cc per sideof test article was placed in the paraspinal bed between the transverseprocesses. Fascia and skin were closed in the routine manner consistentwith good surgical practice. This surgical procedure was then conductedon the contralateral limb using the comparative material. Post-operativecare of the animals was performed in accordance with good husbandrypractices as understood in the art.

No clinical complications were noted in any test group over the courseof the study. Necropsy of the animals was unremarkable regardless oftest group. Macroscopic analysis of the implant sites demonstratedhealthy tissue with no apparent adverse effects such as inflamed,necrotic, or devascularized tissue surrounding the defect sites. Theentire lumbar column was removed “en-bloc”. Soft tissues wereimmediately removed from the surgically treated spinal unit after thespine was dissected out of the body. The grafted site was examined forinfection, and soft tissue abnormalities. Spines allocated for histologyanalysis from the 6 and 12 week animals were placed in 10% neutralbuffered formalin. Spines allocated for biomechanical testing from the12 week animals were tested immediately.

Radiographs at 6 and 12 weeks showed a normal healing response over timein both groups with a loss of graft distinction at the host bonemargins, indicating a progression in host integration and new boneformation over time. No fractures, osteolysis, or other adversereactions were evident during radiographic examination for either group.The radiographs were also assessed for fusion by two reviewers blindedto the treatment groups. The fusion masses in each animal weredetermined to either have bilateral bridging bone, unilateral bridgingbone, no bone on either side, or indeterminate. Fusion success wasdefined by the presence of bilateral bridging bone, indicating bothsides of the spine were fused. At 12 weeks the radiographic fusion rateswere 60% (6/10 animals) for animals implanted with a bone graftcomposition of the present disclosure, and 50% (5/10 animals) for thecomparative material.

The MicroCT scans supported the radiographic findings, showing a normalhealing response over time with no adverse reactions for both testgroups. The 6 week microCT scans showed host integration and new boneformation originating from the defect margins at the TPs in both groups.The 12 week scans showed a progression of new bone formation from acrossthe defect from the 6 week time point. New bone formation was apparentin direct apposition to and bridging between implant granules.

There was a pronounced change in granular surface appearance in thebiphasic granules of the present disclosure's compositions that was lessapparent in the silicate-substituted hydroxyapatite comparativematerial, indicating the more optimal resorption and remodeling responseachievable with a moldable bone graft composition according to thepresent disclosure.

Bilateral, microCT morphometry analysis was performed on sagittal viewscans using a rectangular region of interest (ROI) of 250 mm2 placedacross the fusion site inclusive of the transverse processes and alongthe central axis of the fusion mass. Areas of new bone and residualimplant were calculated based on validated contrast parameters. At 6weeks, the bone graft of the present disclosure demonstratedsignificantly greater bone area (49 vs. 31 mm2; p<0.05) andsignificantly lesser implant area (27 vs. 39 mm2; p<0.05) than thecomparative group. The greater bone area measured in the bone graft ofthe present disclosure is likely due to the bioactive response elicitedby the bioactive glass component. The lesser residual implant areameasured in the present disclosure's bone graft is likely due to rapiddissolution and remodeling of the bioactive glass component and thesolubility of the β-TCP portion of the biphasic mineral componentcompared to the limited resorption capability of the HA-basedcomparative material.

At 12 weeks, there were no statistical differences between the groupsfor either new bone or residual implant areas. However, although theoverall morphometric area for bone was similar between groups at 12weeks, differences in the physical structure of the remodeling bone andoverall progression of defect healing were observed between the testgroups. As remodeling progresses, bone will condense and aligndirectionally according to stress across the defect. For example, thebone graft of the present disclosure demonstrated more condensed andaligned mature bone spanning between TPs, with developed marrow spacesthroughout the material and defect in most animals. Conversely, thecomparative group demonstrated a progression of less condensed immaturebone from the margins of the TPs with less developed marrow spaces. Newbone formation was not observed spanning the TPs in most animals in thecomparative group.

Stiffness of the fused motion segment was assessed by biomechanicalnon-destructive stiffness testing was performed following manualpalpation in the 12 week animals. Testing consisted offlexion/extension, lateral bending, and torsion to a pre-determined,sub-failure load. The vertebral bodies cranial and caudal to the fusedmotion segment were mounted in a biaxial servo-hydraulic materialstesting machine retrofitted with two spine gimbals and a passive XZtable. Custom-made rigid body markers were placed on each vertebral bodyand the two gimbals to track the segmental motions. Nondestructiveflexibility tests were performed about each axis of rotation (i.e.,flexion-extension, right-left lateral bending, and right-left axialrotation) by applying an isolated ±0.27 Nm moment about each of theprimary axes. Each test initiated and concluded in the neutral positionwith zero load. Three loading and unloading cycles were performed withmotion data collected on the third cycle. The displacement of eachvertebrae was measured using an optoelectronic motion capture system,the output of which was synchronized with that of the MTS. Duringtesting, the specimens were kept moist with saline solution spray.Stiffness was determined and compared to normal controls.

At 12 weeks all groups demonstrated significantly less range of motionin all planes compared to normal unfused controls. The biomechanicalfusion rate for each group was determined from the flexion-extensiondata based on work by Erulker et al., who determined a total range ofmotion (ROM) in flexion-extension of less than 5 degrees correlates tosolid fusion in autograft treated specimens in a PLF rabbit model. See,Erulker J S, Grauer J N, Patel TC, Panjabi M M. Flexibility analysis ofposterolateral fusions in a New Zealand white rabbit model. Spine (PhilaPa. 1976). 2001 May 15, 26(10):1125-30.

This ROM threshold also holds clinical significance, as clinical studieshave utilized lateral flexion-extension radiographs where less than 5degrees is utilized as positive threshold for fusion. See, James Kang,MD, Howard An, MD, Alan Hilibrad, MD, Tim Yoon, MD, PhD, Eoin Kavanagh,MD, Scott Boden, MD. Grafton and Local Bone Have Comparable Outcomes toIliac Crest Bone in Instrumented Single-Level Lumbar Fusions. Spine.2012, 37:1083-1091.

Because autograft is considered the “gold standard” treatment forposterolateral spine fusion, and due to the clinical relevance ofevaluating fusion via flexion-extension ROM, specimens with a ROM ofless than 5 degrees in flexion-extension were determined to be “Fused”by biomechanical analysis.

The bone graft of the present disclosure demonstrated a biomechanicalfusion rate of 89% (8/9 animals), while the comparative materialdemonstrated a fusion rate of 44% (4/9 animals).

Of significant note, is that the 80% fusion rate demonstrated by a bonegraft of the present disclosure is higher than the 63% (5/8 animals)fusion rate reported by Erulker et al. for ICBG autograft, consideredthe “gold standard” in the clinical setting.

Histopathology analysis of the decalcified paraffin embedded, H&Estained fusion sites indicated no adverse reactions and a normal healingresponse over time in both groups. The majority of the fusion sites,regardless of implant type or time of implantation, had minimalinflammation. Most often there were very low numbers of macrophages andmultinucleated giant cells (which in some cases could be osteoclasts)with some scattered, often rare lymphocytes and plasma cells. In allsections there is moderate neovascularization and fibrosis. Most of thetissues had moderate new bone formation. New bone formation was notspecifically scored, but at both the 6 and 12 week time points itappeared that the bone graft of the present disclosure had the mostabundant new bone formation and remodeling as opposed to the comparativematerial. This is likely due to the rapid dissolution and remodeling ofthe bioactive glass component, which appeared to have been resorbed andreplaced by mature host bone at 12 weeks. The biphasic HA/β-TCP granulesappeared to be remodeling based on changes in granular appearance andloss of distinction at the new bone interface over time, which were notas apparent in the HA-based comparative material.

In the bone grafts of the present disclosure, at 6 weeks, there was noevidence of acute inflammation and the primary cell types present at theimplant sites were that of macrophages and giant cells with fewerlymphocytes and plasma cells. These cell types were most likely presentto clean up debris associated with the surgery site. The giant cellswere commonly associated with the implant and/or new bone so thereforecould be osteoclasts. There was moderate, to sometimes abundant, fibrousconnective tissue along with neovascularization, which is not surprisingand likely served as a scaffold for new bone formation.

In the bone grafts of the present disclosure, at the 12 week time point,there was a similar pattern of mild to moderate inflammatory cellinfiltrates, with macrophages and giant cells predominating along withfewer numbers of scattered lymphocytes and plasma cells. The increase inmacrophages and giant cells from the 6 week time point is likely due tobone and/or tissue remodeling. There were certainly more giant cellsassociated with new bone and/or implant material suggestive ofosteoclast remodeling. In light of this, there are an increased numberof macrophages to clean up associated cellular debris. Again,neovascularization and fibrosis are expected and the score is similar tothat at 6 weeks.

Bilateral, histomorphometry analysis was performed on calcified plasticembedded, H&E stained sections using a rectangular region of interest(ROI) of 85.8 mm2 placed across the middle of the fusion site between,but not inclusive of, the transverse processes, and along the centralaxis of the fusion mass. Areas of new bone and residual implant werecalculated based on validated color pixel parameters.

The 1 day images showed the defect margins and presence of the implantmaterials with no adverse reactions. At 6 weeks, the bone graft of thepresent disclosure demonstrated significantly greater bone area (25 vs.21 mm2; p<0.05), and significantly lesser implant area (15 vs. 19 mm2;p<0.05) than the comparative group.

The greater bone area measured in the bone graft of the presentdisclosure is likely due to the dissolution and bioactive responseelicited by the bioactive glass component and the gradual remodelingproperties of the biphasic granules. The lesser residual implant areameasured in the bone graft of the present disclosure is likely due torapid dissolution and remodeling of the bioactive glass component andthe solubility of the β-TCP portion of the biphasic mineral component,compared to the limited resorption capability of the HA-basedcomparative material.

At 12 weeks, there were no statistical differences between the groupsfor either new bone or residual implant areas. However, although theoverall morphometric area for bone was similar between groups at 12weeks, differences in the physical structure of the remodeling bone andoverall progression of defect healing were observed between the testgroups. As remodeling progresses, bone will condense and aligndirectionally according to stress across the defect. For example, thebone graft of the present disclosure demonstrated more condensed andaligned mature bone spanning between TPs, with developed marrow spacesthroughout the material and defect in most animals. Conversely, thecomparative group demonstrated a progression of less condensed immaturebone from the margins of the TPs with less developed marrow spaces. Newbone formation was not observed spanning the TPs in most animals in thecomparative group as shown in FIG. 7 .

Also of significant note, in a prior study by this group using the sameanimal model, 45S5 bioactive glass used alone was demonstrated to lacknew bone formation spanning the TPs in all animals.

Example 8—Osteostimulatory Effects

The osteostimulatory effect of the present moldable bone graftcomposition was evaluated using the currently accepted definition ofincreasing osteoblast-like cell proliferation and differentiationtowards a more osteoblastic fate. See, e.g. FIG. 9 .

In the proliferation assay both MG63 and Saos-2 osteoblast-like celllines were cultured with or without the presence of conditioned media.This media was created by first weighing out about 1 g of material forevery 100 ml of media for a 1% solution. The material was washed withPBS twice for 20 min. The material was then equilibrated in DMEM at 37°C. for 24 hours. The solutions were pH adjusted to 7.4 and then filteredthrough a 0.22 μm sterile filter.

It was shown that Saos-2 cell proliferation was significantly increasedwhen cultured in the conditioned media with respect to the control atboth 1 and 3 day time points. Proliferation was also increased withrespect to 45S5 Bioactive Glass as well as the Biphasic granule, butonly significantly at day 1. The MG63 cell line also showed astatistically significant increase in proliferation measured at 3 daysin two different seeding densities. Proliferation was quantified used anMTT assay.

In the differentiation assay both MG63 and C2C12 cell lines werecultured with or without the presence of conditioned media created bythe method earlier explained. It was shown that MG63 cells upregulatedALP activity, a sign of osteoblast differentiation, at 14 and 21 daysalthough only statistically significantly so at 21 days. The C2C12 cellline showed statistically significant ALP upregulation at 7 days incomparison to both the control and the biphasic mineral and an increasecompared to control at day 14, but that increase was not significant.ALP levels were quantified in the cell lysate and normalized to proteinlevels in each condition.

Example 9—Anti-Microbial Effectiveness

The antimicrobial properties of the present moldable bone graftcomposition were evaluated by performing the USP 51 AntimicrobialEffectiveness Test.

To measure the antimicrobial properties of the device a solution of 1 gof material to lml of simulated body fluid (the same as cited in example5) is inoculated with 1×10⁵ to 1×10⁶ Colony Forming Units. After 1, 7,14, and 28 days the samples are assayed for their total colony formingunits.

The bone graft decreased the colony forming units of all organismsthroughout the course of the study satisfying the category 1 acceptancecriteria of USP 51. See, e.g. FIG. 10 .

Although various embodiments have been described as having particularfeatures and/or combinations of components, other embodiments arepossible having any combination or sub-combination of any featuresand/or components from any of the embodiments described herein. Thespecific configurations of the various components can also be varied.For example, the size and specific shape of the various components canbe different than the embodiments shown, while still providing thefunctions as described herein.

Thus, the breadth and scope of the disclosure should not be limited byany of the above-described embodiments, but should be defined only inaccordance with the following claims and their equivalents. The previousdescription of the embodiments is provided to enable any person skilledin the art to make or use the disclosure. While the disclosure has beenparticularly shown and described with reference to embodiments thereof,it will be understood by those skilled in the art that various changesin form and details may be made therein without departing from thespirit and scope of the disclosure.

INCORPORATION BY REFERENCE

All references, articles, publications, patents, patent publications,and patent applications cited herein are incorporated by reference intheir entireties for all purposes. However, mention of any reference,article, publication, patent, patent publication, and patent applicationcited herein is not, and should not be taken as, an acknowledgment, orany form of suggestion, that they constitute valid prior art or formpart of the common general knowledge in any country in the world.

What is claimed is:
 1. A moldable bone graft composition, comprising: a)one or more bioresorbable polymers; b) biphasic calcium phosphateparticles comprising hydroxyapatite and tricalcium phosphate; and c) abioactive glass component, wherein said biphasic calcium phosphateparticles and said bioactive glass together comprise about 10-70% byweight of the moldable bone graft composition.
 2. The moldable bonegraft composition of claim 1, wherein the bioactive glass componentcomprises about 1-40% by weight of the moldable bone graft composition.3. The moldable bone graft composition of claim 1, wherein the one ormore bioresorbable polymers comprise a polyalkylene oxide polymer havingat least one of the following: a molecular weight of about 500-1500grams/mole; a specific gravity of about 1.0-1.3 (at 25° C.); a viscosityof about 10-40 cSt (at 210° C.); or a melting temperature of about38-50° C.
 4. The moldable bone graft composition of claim 1, wherein thebiphasic calcium phosphate particles comprise about 20-60%hydroxyapatite and about 40-80% tricalcium phosphate.
 5. The moldablebone graft composition of claim 1, wherein the biphasic calciumphosphate particles have interconnected macro- and microporosity.
 6. Themoldable bone graft composition of claim 1, wherein about 30-90% of thebiphasic calcium phosphate particles have a particle size of about1000-2000 μm; about 10-70% of the biphasic calcium phosphate particleshave a particle size of about 425-1000 μm, about 10-50% of the biphasiccalcium phosphate particles have a particle size of about 710-1000 μm;and about 1-30% of the biphasic calcium phosphate particles have aparticle size of about 425-710 μm.
 7. The moldable bone graftcomposition of claim 1, wherein the bioactive glass comprises 45S5bioactive glass.
 8. The moldable bone graft composition of claim 1,wherein the bioactive glass is in the form of particles having aparticle size of about 1-600 μm.
 9. The moldable bone graft compositionof claim 1, wherein the bioactive glass is in the form of particleshaving a particle size of about 1-425 μm.
 10. The moldable bone graftcomposition of claim 1, wherein at least 80% of the bioactive glass isin the form of particles having a particle size of about 212-425 μm. 11.The moldable bone graft composition of claim 1, wherein the bioactiveglass is in the form of irregular granules.
 12. The moldable bone graftcomposition of claim 1, wherein the bioactive glass is in the form ofapproximately spherical particles.
 13. The moldable bone graftcomposition of claim 1, wherein the bioactive glass is in the form offibers.
 14. The moldable bone graft composition of claim 1, whereinabout 60-90% of the biphasic calcium phosphate particles and bioactiveglass together are in the form of particles having a particle size ofabout 425-2000 μm, and about 10-40% of the particles have a particlesize of about 1-425 μm.
 15. A single use moldable bone graft compositionof claim 1, having a mass of about 1.5-30 grams.
 16. A single usemoldable bone graft composition of claim 1, having a volume of about1-20 cc.
 17. The moldable bone graft composition of claim 1, having adensity of about 1.2-1.8 g/cc.
 18. The moldable bone graft compositionof claim 1, in the form of a cylinder.
 19. The moldable bone graftcomposition of claim 18, wherein said composition has a crush resistanceforce of less than about 20 lbf.
 20. The moldable bone graft compositionof claim 1, wherein said composition can be molded into any desiredshape without loss of homogeneity.
 21. The moldable bone graftcomposition of claim 1, having a cubical shape.
 22. A syringe applicatorfilled with the moldable bone graft composition of claim
 1. 23. Thesyringe applicator of claim 22, wherein the force required to eject themoldable bone graft composition from the syringe applicator is less than20 lbf.
 24. The moldable bone graft composition of claim 1, furthercomprising: a melt skin layer disposed on the outer surface of thecomposition, wherein the melt skin layer comprises the bioresorbablepolymer.
 25. The moldable bone graft composition of claim 1, wherein thebioresorbable polymer dissolves in PBS at 37° C. at a rate of about0.01-0.20 grams/minute.
 26. The moldable bone graft composition of claim1, wherein the bioresorbable polymer dissolves in PBS at 37° C. in about60-600 minutes.
 27. The moldable bone graft composition of claim 1,wherein the bioresorbable polymer dissolves in PBS at 37° C. in lessthan 60 minutes.
 28. The moldable bone graft composition of claim 1,wherein the composition is supplied with, or used in conjunction with,allograft tissue.
 29. The moldable bone graft composition of claim 1,wherein the moldable bone graft composition forms a hydroxyapatitesurface layer in simulated body fluid.
 30. The moldable bone graftcomposition of claim 1, wherein the moldable bone graft compositionstimulates mesenchymal stem cell differentiation in a cell cultureassay.
 31. The moldable bone graft composition of claim 1, wherein themoldable bone graft composition stimulates osteoblast cell proliferationin a cell culture assay.
 32. The moldable bone graft composition ofclaim 1, wherein the moldable bone graft composition demonstrates anantimicrobial efficacy according to methods based on USP <51>.
 33. Themoldable bone graft composition of claim 1, wherein the moldable bonegraft composition stimulates mesenchymal stem cell differentiation andosteoblast cell proliferation in a cell culture assay and demonstratesan antimicrobial effect.
 34. The moldable bone graft composition ofclaim 1, wherein the moldable bone graft composition provides a spinefusion rate of greater than or equal to 50% in a New Zealand whiterabbit spine fusion model.
 35. A method for repairing a bone defect,comprising: applying the moldable bone graft composition of claim 1 to abone defect in a patient in need thereof.
 36. The method of claim 35,wherein the bone defect is a spinal bone defect.
 37. The method of claim35, wherein the bone defect is in the posterolateral gutter of avertebral body.
 38. The moldable bone graft composition of claim 1,wherein the composition is supplied with, or used in conjunction with,xenograft tissue.
 39. The moldable bone graft composition of claim 1,wherein the moldable bone graft composition is osteoinductive.